title: Taper design affects failure of large-head metal-on-metal total hip replacements.
abstract: BACKGROUND
  Large-head metal-on-metal (MoM) hip arthroplasties have demonstrated poor survival. Damage at the taper-trunnion junction is a contributing factor; however, the influence of junction design is not well understood.
  
  
  OBJECTIVE
  (1) Does taper type affect fretting, corrosion, and volumetric wear at the junction? (2) Do taper types have different wear patterns? (3) Does larger offset or head diameter increase fretting, corrosion, and wear? (4) Is the extent of fretting and corrosion associated with earlier failure?
  
  
  METHODS
  Taper damage in 40 retrieved heads was subjectively graded for fretting and corrosion, and wear was determined with high-resolution confocal measurement. Taper types (11/13, 12/14, and Type 1) differed by angle, distal diameter, and contact length; Type 1 were thinnest and 11/13 had longer contact lengths.
  
  
  RESULTS
  Fretting scores were higher in 11/13 than in Type 1 tapers. Volumetric wear and wear rates did not differ among types. Uniform, circumferential, and longitudinal wear patterns were observed in all types, but fretting, corrosion, and wear did not differ among the patterns. Head diameter and lateral offset did not correlate with fretting, corrosion, or wear. No correlation was found between fretting, corrosion, or wear and length of implantation.
  
  
  CONCLUSIONS
  In general, thicker tapers with longer contact lengths were associated with greater fretting scores, whereas no relationship was found among the three designs for corrosion scores or volumetric wear. This finding suggests that trunnion diameter and engagement length are important factors to consider when improving taper-trunnion junction design.
authors.affiliation: Department of Orthopedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA, nnassif@post.harvard.edu.
authors.forename: Nader A
authors.initials: NA
authors.lastname: Nassif
authors.forename: Danyal H
authors.initials: DH
authors.lastname: Nawabi
authors.forename: Kirsten
authors.initials: K
authors.lastname: Stoner
authors.forename: Marcella
authors.initials: M
authors.lastname: Elpers
authors.forename: Timothy
authors.initials: T
authors.lastname: Wright
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Padgett
mesh_terms: D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D020878:Device Removal; D005260:Female; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D016014:Linear Models; D008297:Male; D061825:Metal-on-Metal Joint Prostheses; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies; D013314:Stress, Mechanical; D016896:Treatment Outcome